You’ve probably seen reports and images circulating in the news showing power outages, brownouts, and blackouts resulting from our ever-increasing energy demands. Perhaps you’ve even experienced one of these power outages personally. Now imagine the unanticipated consequences of an outage if critical life-saving medical equipment suddenly lost power, or a businesses’ core data servers ceased functioning without the use of backup power. The technology that keeps these critical resources running during a power outage would not be possible without the use of high-rate battery technology.
High Rate Battery Definition
So, what exactly qualifies a battery as a “High-Rate” battery and what specific characteristics make it unique when compared to a “Deep Cycle” battery?
Simply defined, a high-rate battery is engineered to store energy and release large bursts of that stored energy in a very short period of time. To fully grasp the technology that makes them unique, you must first understand the relationship between the battery’s C Rating and its’ discharge.
C Ratings are the measurement of current in which a battery is charged and discharged at. Therefore, a high-rate discharge application would require a battery designed to deliver high C rates or release large amounts of constant energy over a few minutes. This differs from a deep discharge battery, which is built to deliver steady power over a longer period.
As an example, consider two vehicles, a finely tuned sport racing vehicle designed to run at a high speed on a short track and a passenger car intended to drive cross country. Each vehicle has a very specific purpose, one is intended to reliably output high power in short distance while the other offers a reliable and consistent speed over a long period of time. Similarly, high-rate batteries are used in specific applications that exert a massive amount of energy quickly. Although similar in appearance, the key difference between these two batteries lies in the assembly and number of lead plates.
High-rate SLA Battery Construction
Within every lead acid battery, there exists some form of lead (electrodes) and sulfuric acid (electrolyte). The way in which lead plates are arranged and constructed directly correlates to the amount of energy a battery can release. In the case of high-rate batteries, the lead plates are designed to be thinner than that of a deep-cycle battery. With thinner plates, there is extra space for additional lead plates. The extra lead increases the overall surface area of the active electrode material, which in turn increases the chemical reaction that takes place with the electrolyte (sulfuric acid). The result is a battery capable of rapidly releasing large amounts of energy to the terminals on demand.
High discharge models are particularly important in backup power applications, where consistent energy is needed to keep power running during outages. Security, medical, industrial, telecommunications, and data processing industries regularly implement high-rate battery systems for lossless power during an outage. Businesses regularly rely on these batteries to prevent power disruptions to fire alarms, emergency lighting, security cameras, network servers, IT systems, and process control systems. In these standby applications, sealed lead-acid batteries are an ideal choice due to their low cost, low maintenance, and reliability in float mode. Since these batteries are only used for short periods of time, the majority of their lifespan is spent in float mode. In standby applications, it is critical the batteries are charged and ready to provide on-demand energy. To maintain this constant state of charge, lead-based batteries uniquely require what is called a float charge or maintenance charge. During this charging mode, the battery receives a constant voltage and limits the initial charge current. For all batteries careful notice should be applied to charging, incorrect charging habits or techniques can either cause a battery’s failure or shorten their lifespan.
Lithium High-rate Batteries
In addition to backup power and uninterruptable power systems (UPS), high-rate technology has become increasingly important in consumer and other high-powered products. With an ability to deliver continuous power during discharge and boasting a lower weight than their SLA counterparts, lithium batteries are critical in high-power, mobile applications.
Lithium high-rate batteries are constructed with power cells. Power cells are designed to deliver high current loads over a short period of time. Lithium is an extremely powerful chemistry that is able to exert continuous power on demand no matter the state of charge. Power-Sonic power cells like the PSL-FP-IFR26650PC can support as much as a 22 Watts all by itself! However, the BMS (Battery Management System) or protection boards may limit the energy able to be released as the components designed to offer protections can only handle so much current. Power-Sonic lithium batteries are design with protection circuits that can easily take on these high-rate situations. The PSL-SC-1270, for example, can discharge at an astonishing 48 Watts per cell versus it’s SLA counterpart that is rated to only 36 W/cell. That’s 130% the power with the added benefits of lithium – like significantly longer life while being much lighter!
Although many high-rate applications utilize a stationary battery, a growing number of applications require a power solution that is light weight and portable. Lithium excels in high-powered products such as aerial drones, robotics, power tools, portable power stations, vehicle jump starters, etc.
Watts per Cell
When choosing a high-rate battery for your application, it is important to evaluate the discharge time required, environmental temperatures, electrical load requirements for power and energy, overall battery life required, and if the battery will be stationary or mobile. It is common for high-rate batteries to identify their nominal power in watts per cell. The watts per cell (W/cell) method identifies the total power a battery cell can safely exert during a set time interval, i.e., 15-20 minutes. It is calculated as follows:
(Volts [of application] X Amps [needed for application])/ number of cells
Whether used to temporarily power a home office or provide uninterrupted power to a factory’s critical systems, high-rate batteries are everywhere around us. The next time you are in the store, working in the office, or visiting the doctor’s office, take note of all the critical equipment used and how significant of a role high-rate batteries play in keeping the power on.
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